Aw, I'm really sorry Jalal. Can you do a water test and let us know what the levels are? Do you think you hd a power outage?

I did a 30% water change the same day--did not test water but put prime in which will give false readings. Because the fluval filter (its an XP450 or something like that) wasn't working this morning I am suspicious that it had stopped maybe a power outage and then started back up. When I did the water change that day and cleaned the filter/pump tank it ran noisy after cleaning. I didn't have an air bubbler in the tank as it made the fluval seem to run air. This pump/filter pumps water back into the tank at 950GPH so was putting alot of water agitation/oxygen back in the water. However I had not fed the fish in 5 days before Saturday and had not done a water change in a month. With so many dead at once it had to have been ammonia or the pump going off. I have a small aquarium bubbler running on the tank now but with only 3 fish left. When the pump was off this morning I took it apart and cleaned it as it was quite dirty. I'm afraid I just wasn't taking good care of my fish. I work straight nights now 6 days in a row with 10 hour shifts on the weekends and have not been as diligent on the care of my fish. Lesson learned the hard way! The white sarassa comets that died were very pink which also makes me think ammonia. They were beautiful fish white with orange heads and very long tails. I've had them for six years and have not seen sarassa's in pet stores since I bought them.

Sorry for your loss. It can be devastating.
20 fish in 300 gal of water may have been too much but ammonia or a bad pump the outcome still sucks.
Mike

Thanks Mike and zinnia. Yes it does suck when you've had the fish for a long time. I talked to my water garden store tonight and they have some shubunkins and goldfish for sale. They aren't that big 4" but I bought most of my fish from them when I started out and the shubunkins that survived came from them last year. They are going out of business unfortunately as her husband has cancer. That is a lot sadder than my fish loss.

Ah that is heartbreaking, sorry about your fish lose.

Craig

Hi Jalal. I'm so sorry to hear about the loss of your fish. Is this the first time you have kept your fish inside?

The first thing I would do would be to make a one third water change from the bottom of your pond and increase the size of your pond or tank. I suspect there were way too many fish in the pond/tank and that is the reason for the fish deaths.
I've got a great diagram for a bio-filter that is easily made and we can keep in touch to if you have any questions. I have some young Koi downstairs that I over wintered and they all came through the winter well. The pond is about 160 gallons and I have a 25 gallon bio-filter on it to keep them healthy.
The secret to keeping Koi and Goldfish indoors in tanks is to make those every two weeks water changes from the bottom and to make sure that you have a good bio-filter.

Your's Koily, Lorraine

Thanks everyone for replies. Yes I bring my fish in every year and I have lost one or two within a week of bringining them in before. These were fish that didn't look too good when they were brought in as I usually wait until the water is about 45F or less before ice. Two days after the fish loss the pump/filter was off so I suspect that is what happened and major loss of oxygen in the water. I did go to my water garden store a week after and bought 12 new fish. Managed to get 3 koi in the batch. They are all small fish under 4 inches but are doing fine. We've had a lot of power outages this spring which may have shut the pump down. Could only get 1 of the white fish with orange heads that I like. I will probably give the koi away as they just get too big and are dirty fish and eat everything in sight. The ones I got look like shubunkins which is why we took them. I will miss the pond store as they are a nice couple. He has cancer throughout his body, even in his bone marrow and all he can do is take morphine for the pain. So sad.
Oh the ice is finally gone from my pond earlier this week. Spring is about two weeks behind here so the fish will be inside this spring for a long time!

Sorry about the fish. Wondering if there is an electronic monitoring solution to prevent this in the future.

I have read you shouldn't move your fish once the water gets below 55 degrees as it causes the fish too much stress, I would think 45 degrees is way too late and stressful. I would move them before then.

How deep is your pond? Why not get a deicer and winter them outside? On garden pond forum there"s a lady who winters her fish outdoors in Alberta Canada.